From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755563AbcBXOPq (ORCPT ); Wed, 24 Feb 2016 09:15:46 -0500 Received: from smtp.citrix.com ([66.165.176.89]:17310 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751814AbcBXOPp (ORCPT ); Wed, 24 Feb 2016 09:15:45 -0500 X-IronPort-AV: E=Sophos;i="5.22,494,1449532800"; d="scan'208";a="334148095" Subject: Re: [Xen-devel] [PATCH] xen/x86: Zero out .bss for PV guests To: David Vrabel , Boris Ostrovsky , References: <1456178767-8038-1-git-send-email-boris.ostrovsky@oracle.com> <56CDBA5A.1000600@citrix.com> CC: , , From: Andrew Cooper Message-ID: <56CDBB0F.9000203@citrix.com> Date: Wed, 24 Feb 2016 14:15:43 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Icedove/38.5.0 MIME-Version: 1.0 In-Reply-To: <56CDBA5A.1000600@citrix.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-DLP: MIA2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 24/02/16 14:12, David Vrabel wrote: > On 22/02/16 22:06, Boris Ostrovsky wrote: >> Baremetal kernels clear .bss early in the boot. Since Xen PV guests don't >> excecute that early code they should do it too. >> >> (Since we introduce macros for specifying 32- and 64-bit registers we >> can get rid of ifdefs in startup_xen()) > .bss must have been cleared for PV guests otherwise they would be > horribly broken. What was the method and why is it no longer sufficient? The domain builder hands out zeroed pages. I don't believe we guarantee that the guests RAM is clean, but it is in practice. ~Andrew